1. Field of the Invention
The present invention relates to a water proof and dust proof structure of a key switch device, which is preferable for use, for example, in mobile communication terminal such as a portable wireless phone or cellular phone.
2. Description of the Prior Art
Recently, accompanied with liberalization of the electric communication business, popularization of various mobile communication terminal including a portable wireless phone or cellular phone has been developed.
Usually, a user puts a mobile communication terminal in a bag or a pocket of clothes and carries it outdoors, and thus, the water proof and dust proof structure has strongly requested for the mobile communication terminal. Particularly, the water proof and dust proof structure is requested for a key switch device of the terminal.
Previously, for the water proof and dust proof structure of a key switch device in this type of a portable wireless phone or cellular phone, a structure has been employed, which includes an instrument case having a key insertion hole open between the inside and outside surfaces of the case and a fitting groove open in the inside opening periphery of this key insertion hole, a key base contained in this instrument case and having a switch contact point portion, a rubber seat provided on the switch contact point portion side of this key base and having a key inserted into the key insertion hole and a switch thrust piece corresponding to the switch contact point portion on the base side, and a spacer provided between this rubber seat and the instrument case and pressing and bringing a seal member into contact with the inside of the fitting groove.
In such a water proof and dust proof structure of a key switch device, the seal member is provided between the instrument case and the spacer in a state of being compressed, and the portable wireless phone or cellular phone is assembled, and the place between the instrument case (seal member) and the spacer and the place between the spacer and the rubber seat are sealed.
However, in this type of water proof and dust proof structure of a key switch device, a seal member and a spacer are provided between the instrument case and the rubber seat, and therefore, there has been such a problem that the number of pieces of parts is increased so that not only the assembly work may become complicated but also the cost may be raised.
Furthermore, in a conventional water proof and dust proof structure of a key switch device, not only a seal member but also a spacer is provided between the instrument case and the rubber seat, and therefore, the pressing and contacting force of the spacer to the seal member becomes insufficient, and in addition, rain water or the like stays in the key insertion hole, so that the water level may be higher than the sealing position between the spacer and the rubber seat at all times, and it has been impossible to maintain the sealing function between the rubber seat and the spacer and the reliability in sealing are reduced. As a result of this, the rain water cannot surely be prevented from reaching electronic parts such as a key base, and there has been a problem of lowering the water proof and dust proof effect.
Herein, Japanese Utility Model Application Laid-Open No. 5-34755 published on May 7, 1993 and Japanese Utility Model Application Laid-Open No. 6-17056 published on Mar. 4, 1994 disclose prior arts as [structure of an operating portion of telephone] and [water proof structure of a keyboard switch], respectively, but the above described problems are not solved.
It is an object to provide a water proof and dust proof structure of a key switch device, by which simplification of the device assembly work and lowering of the cost can be attained, and in the meantime, the water proof and dust proof effect can be raised.
In order to attain the above described object, a water proof and dust proof structure of a key switch device of the present invention includes: an instrument case having a key insertion hole open to the inside and outside of the case; a key base contained in this instrument case and having a switch contact portion; and a key seat which is provided on the key base and which is made of a flexible member having a key inserted into the key insertion hole and a switch thrust piece corresponding to the switch contact portion on the seat surface side and on the seat reverse side, respectively, and it is configured such that a frame-like rib which is pressed and brought into contact with the inside opening periphery of the key insertion hole and which surrounds the side portion of the key is provided integrally to this key seat.
Accordingly, the sealing is performed between the opening end surface of the rib in the key seat and the opening periphery of the key insertion hole in the instrument case.
The water proof and dust proof structure of a key switch device of the present invention may also be configured such that a frame-like rising wall which is positioned inside the rib and which is pressed and brought into contact with the seat surface of the key seat is integrally provided to the inside opening periphery of the key insertion hole.
According to this configuration, in the sealed state, the opening end surface of the rib is pressed and brought into contact with the opening periphery of the key insertion hole, and in the meantime, the opening end surface of the rising wall is pressed and brought into contact with the seat surface side of the key seat.
Furthermore, the water proof and dust proof structure of a key switch device of the present invention may also be configured such that a projection whose wall thickness becomes smaller toward the key seat side from the key insertion hole side is formed at the tip surface of the rising wall.
According to this configuration, in the sealed state, the projection of the rising wall is pressed and brought into contact with the seat surface of the key seat so that it may bite into the seat surface.
Another water proof and dust proof structure of a key switch device according to the present invention includes: an instrument case having a key insertion hole open to the inside and outside of the case; a key base contained in this instrument case and having a switch contact point portion; and a key seat which is provided on the switch contact point portion side of this key base and which is made of a flexible member having a key inserted into the key insertion hole and a switch thrust piece corresponding to the switch contact point portion on the seat surface side and on the seat reverse side, respectively, and it is configured such that a rib and a rising wall surrounding the side portion of the key are integrally provided at the seat surface of this key seat and at the inside opening periphery of the key insertion hole, respectively, and that seal portions which are pressed and brought into contact with each other are provided at the respective tip portions of these rising wall and rib.
Accordingly, in the sealed state, the seal portion of the rib and the seal portion of the rising wall are pressed and brought into contact with each other.
The water proof and dust proof structure of a key switch device of the present invention may also be configured such that each seal portion of the rib and the rising wall is formed by a slant surface.
According to this configuration, in the sealed state, the slant surface of the rib and the slant surface of the rising wall are pressed and brought into contact with each other.
The water proof and dust proof structure of a key switch device of the present invention may also be configured such that one seal portion among the seal portion of the rib and the seal portion of the rising wall is formed by a projection having an approximately half-circular cross section, and that the other seal portion is formed by a projection having an approximately triangular cross section.
According to this configuration, in the sealed state, the respective projections in the rib of the key seat and the rising wall of the instrument case are pressed and brought into contact with each other.